This invention relates generally to a sample collecting system and, more particularly to a sampling apparatus for successively collecting small-volume samples from a fluid stream of factory waste water for example, the flow rate of which varies with time, the volume of the respective collected sample being proportional to the flow rate of the stream during the sample collecting cycle.
Recently the problems relating to public pollution has become so serious that, even with respect to the "control of water quality" of waste water from factories etc., the "control of total amount" is on the verge of being put into practice in place of the conventional "control of concentration". In the case of the control of total amount, it is needed to integrate or continuously add the products of the amount and concentration of waste water during the whole measurement period of time so as thereby to determine the total amount of pollution substance for the given period of time. It would be possible to known the total amount of the pollution substance by continuously measuring and multiplying the amount and concentration of the waste water to provide the integrated value, but in such a case, the apparatus therefor becomes very complicated and expensive.
In order to overcome such disadvantage, a sampling system has been proposed wherein from waste water which is to be subjected to the control of total amount, a small quantity of sample the volume of which is proportional to the flow rate of the waste water is picked up. Such liquid samples are accumulated without change of water quality during a predetermined period, and the amount of pollution substance included in the accumulated liquid sample is measured by using an analyzer, whereby the total amount of the pollution substance which was dashed together with the waste water is estimated. Since according to this system, it is not necessary to simultaneously measure the flow rate and concentration, the apparatus becomes simple, and the total amount of the pollution substance can be ascertained by a simple analyzer, and, accordingly, this system is very promising as a waste water measuring apparatus for small and medium enterprises which cannot afford a heavy equipment investment.
However, since such prior sampling apparatus was one wherein the samples are intermittently collected in proportion to the flow rate of the waste water stream, it could not perform a completely continuous measurement, and especially, in cases where a considerable variation in the quality of the samples exists, the system would possibly produce a great error.